Piston pump for a high-pressure cleaning appliance

ABSTRACT

A piston pump for a high-pressure cleaning appliance is provided, including a plurality of pump chambers into each of which one piston which is movable back and forth plunges, and which are each in flow connection via a suction valve with a suction inlet and via a pressure valve with a pressure outlet, the pistons each being surrounded by a sealing ring which is supported in the radial direction by a ring wall and in the axial direction by a support ring. In order to develop the piston pump in such a way that it can be manufactured and assembled more cost-effectively, it is proposed that the piston pump includes a one-piece support shield which forms the support rings and surrounds the ring walls in the circumferential direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of international application number PCT/EP2012/050867, filed on Jan. 20, 2012, which is incorporated herein by reference in its entirety and for all purposes.

BACKGROUND OF THE INVENTION

The invention relates to a piston pump for a high-pressure cleaning appliance, comprising a plurality of pump chambers into each of which one piston which is movable back and forth plunges, and which are each in flow connection via a suction valve with a suction inlet and via a pressure valve with a pressure outlet, the pistons each being surrounded by a sealing ring which is supported in the radial direction by a ring wall and in the axial direction by a support ring.

A liquid, preferably water, can be pressurized and directed at an article to be cleaned or a surface to be cleaned by means of such piston pumps. For this purpose, the pistons can be reciprocatingly driven, for example, by means of a swash plate, so that the volumes of the pump chambers periodically change and liquid can be drawn from the suction inlet via the suction valves into the pump chambers, pressurized there and discharged via the pressure valves and the pressure outlet. A pressure hose, for example, which carries at its free end a discharge member for the pressurized liquid, for example, a spray nozzle or a spray lance, can be connected to the pressure outlet.

The pump chambers are each sealed by means of a sealing ring which surrounds the piston plunging into the pump chamber in the circumferential direction. The sealing ring can form a sealing lip, for example, which under the pressure prevailing in the pump chamber is pressed against the lateral surface of the piston. The sealing ring is usually supported by a ring wall in the radial direction, and a support ring is usually used for support in the axial direction. Such piston pumps are known, for example, from DE 44 45 519 C1.

In many cases, the liquid is pressurized in the pump chambers to a pressure above 100 bar. While in operation, the piston pump is, therefore, subjected to considerable mechanical stresses and must have a high mechanical stability. The piston pumps, therefore, usually have a substantial material thickness. This involves not inconsiderable manufacturing costs. Furthermore, the relatively high material thickness has the consequence that the housing of the piston pump, which is usually manufactured in a casting process, undergoes a lengthy cooling process during the manufacture, which limits the production rate of the housing. This also increases the manufacturing costs of the piston pump.

The object of the present invention is to develop a piston pump of the kind mentioned at the outset in such a way that it can be manufactured more cost-effectively.

SUMMARY OF THE INVENTION

This object is accomplished, in accordance with the invention, in a piston pump of the generic kind in that it comprises a one-piece support shield which forms the support rings and surrounds the ring walls in the circumferential direction.

In the piston pump in accordance with the invention, all of the support rings which support in the axial direction the sealing rings surrounding one piston each in the circumferential direction are integrated in a one-piece support shield. This makes simpler assembly of the piston pump possible as all of the support rings can be positioned in a single assembly step.

The one-piece support shield used in accordance with the invention has, in addition, the function of surrounding the aforementioned ring walls in the circumferential direction and, therefore, supporting the ring walls in the radial direction. This allows the material usage for the ring walls to be reduced as the resulting reduction in the mechanical stability of the ring walls is compensated by the support shield surrounding all of the ring walls in the circumferential direction.

The one-piece support shield, therefore, makes it possible to reduce the material usage for the pump housing and to simplify the assembly of the piston pump.

In an advantageous embodiment, the support shield comprises a plurality of support sleeves into each of which a ring wall extends. As explained above, the pump chambers are sealed by means of the sealing rings which surround one piston each and, in turn, are surrounded by a ring wall and are supported on a support ring in the axial direction. In the advantageous embodiment of the invention, the ring wall extends into a support sleeve which is defined by the one-piece support shield.

It may, for example, be provided that the piston pump in accordance with the invention comprises three pistons which plunge into one pump chamber each, each pump chamber having a ring wall associated therewith, which supports a sealing ring in the radial direction and extends into a support sleeve of the support shield. In such a configuration, the ring wall can be of particularly thin-walled construction and yet the liquid to be pumped can be pressurized in the pump chambers to a high pressure.

In a particularly preferred configuration of the invention, the piston pump comprises a pump block which includes the pump chambers and is connected to the support shield by substance-to-substance bonding. This allows the manufacturing costs to be additionally reduced and the assembly of the piston pump to also be simplified.

An adhesive connection, for example, can be used as substance-to-substance bonded connection. A layer of adhesive can, for example, be provided between the ring walls surrounding one sealing ring each in the circumferential direction and the support shield surrounding the ring wall in the circumferential direction. This makes a connection between the pump block and the support shield possible, which is able to withstand mechanical stress. The layer of adhesive can additionally serve as sealing element for the liquid to be pumped. A uniform distribution of tension and transfer of force can also be achieved by the adhesive connection. Tension peaks, as may often occur with a screw connection, can be reduced.

In a particularly preferred embodiment of the invention, the pump block is welded to the support shield. This makes a connection possible, which has a particularly high resistance to stress and also reliably withstands very high pressures.

It is expedient for the ring walls surrounding one sealing ring each in the circumferential direction to each be welded to a surrounding support sleeve.

The pump block and the support shield are preferably made of a plastic material. This allows the pump block to be connected to the support shield by, for example, ultrasonic welding. If the support shield comprises support sleeves, as explained hereinabove, the support sleeves can be fitted on one ring wall each and welded to it in a constructionally simple way. The welded connection makes it possible for the two parts to be permanently fixed to each other so that they are subsequently unable to execute any relative movement. As optimum sealing can also be achieved with the welded connection, additional seals between the two parts can be dispensed with.

It is advantageous for the support shield to be fitted on a guide shield comprising guide members for guiding the pistons in the axial direction. The pistons can be guided in the axial direction by means of the guide members of the guide shield. The guide shield simultaneously has the function of supporting the support shield in the axial direction.

It may, for example, be provided that the support shield comprises support collars preferably aligned coaxially with the support sleeves. The support collars are fitted on the guide shield and surround one piston each in the circumferential direction. The support shield can be supported on the guide shield in a constructionally simple way by means of the support collars. In addition, the use of the support collars has the advantage that the mechanical stability of the support shield is increased, with the material thickness of the support shield being able to be kept relatively low.

The support collars preferably comprise one drainage opening each, for example, a drainage slot. Liquid leaking inadvertently from the pump chambers via the sealing ring surrounding one piston each can be discharged to the environment via the drainage opening.

In a particularly preferred embodiment of the invention, a particularly high mechanical stability with relatively low material usage can be achieved by the support shield being supported by a guide shield of convex shape, which forms a cover for a swash plate housing. In such a configuration, the guide shield supporting the support shield in the axial direction is of convex construction. This imparts a particularly high mechanical stability to it and allows the material thickness of the guide shield to be reduced. In addition to its function of guiding the pistons in the axial direction and supporting the support shield in the axial direction, in such a configuration, the guide shield assumes the function of a cover for the swash plate housing in which a swash plate is arranged, with which the pistons interact in order to bring about a reciprocating movement. The swash plate can be rotated about the longitudinal axis of the piston pump, and the pistons can be driven by the rotational movement of the swash plate so as to move back and forth, under the action of which the volumes of the pump chambers are periodically changed.

The following description of a preferred embodiment of the invention serves for further explanation in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic longitudinal sectional view of an advantageous embodiment of a piston pump in accordance with the invention;

FIG. 2 shows a plan view of a pump block, welded to a support shield, of the piston pump from FIG. 1;

FIG. 3 shows a sectional view of the pump block, welded to the support shield, along line 3-3 in FIG. 2; and

FIG. 4 shows a sectional view of the pump block and the support shield in the manner of an exploded drawing.

DETAILED DESCRIPTION OF THE INVENTION

An advantageous embodiment of a piston pump in accordance with the invention, generally denoted by reference numeral 10, is shown schematically in the drawings. The piston pump 10 comprises a pump head 12 with a suction inlet 14, via which a liquid to be pressurized, preferably water, can be supplied to the piston pump 10. A supply line, for example, can be connected to the suction inlet 14. The pump head 12 also comprises a pressure outlet 16 via which the pressurized liquid can be discharged. A pressure hose, for example, carrying at its free end a discharge member for the pressurized liquid, for example, a spray lance or a spray nozzle can be connected to the pressure outlet 16.

The pump head 12 is fitted in the axial direction, in relation to a longitudinal pump axis 18, on a pump block 20 comprising a plurality of pump chambers 22, into each of which one piston 24 plunges. The piston pump 10 shown in the drawings has a total of three pump chambers. Only one pump chamber 22 is recognizable in the drawings. The pump chambers are arranged so as to be uniformly distributed about the longitudinal pump axis 18 and are each at the same radial distance from the longitudinal pump axis 18.

The pump chambers 22 are each in flow connection via a suction valve 26 with the suction inlet 14 and via a pressure valve 28 with a central pressure chamber 30, which the pump head 12 and the pump block 20 form between them. Adjoining the pressure chamber 30 in the axial direction is a pressure line 32, aligned coaxially with the longitudinal pump axis 18, via which the pressure chamber 30 is in flow connection with the pressure outlet 16.

A central insert part 34 formed rotationally symmetrically in relation to the longitudinal pump axis 18 is held in the pressure chamber 30. The insert part 34 is formed in the manner of a piston and is surrounded by two sealing rings arranged between the insert part 34 and the wall of the pressure chamber 30. The insert part 34 forms a holding element for closing springs 40 of the pressure valves 28. On its front side that faces away from the closing springs 40, the insert part 34 has a recess 42 into which a closing member 44 of a central check valve extends, by means of which a central passage of the insert part 34 can be closed.

The pump chambers 22 are each sealed in the direction facing away from the pump head 12 by means of a sealing ring 46 which has a sealing lip 48 and surrounds a piston 24 in the circumferential direction. The sealing ring 46 is surrounded in the circumferential direction by a collar-like ring wall 50 of the pump block 20. The ring wall 50 is of cylindrical construction and is aligned coaxially with a longitudinal piston axis 52. In relation to the longitudinal piston axis 52, the ring wall 50 supports the sealing ring 46 radially.

On the side that faces away from the pump head 12, the pump block 20 is adjoined by a one-piece support shield 54 whose configuration is evident, in particular, from FIG. 4. It comprises support rings 56 which support one sealing ring 46 each in the axial direction. Each support ring 56 is adjoined by a cylindrical support sleeve 58 which is aligned coaxially with a longitudinal piston axis 52 and surrounds a ring wall 50 in the circumferential direction. On the rear side that faces away from the support shields 54, the support shield 54 carries a plurality of cylindrical support collars 60 which are also aligned coaxially with the longitudinal piston axes 52 and have one drainage opening each in the form of a drainage slot 62.

The support shield 54 is of one-piece construction and is made of a plastic material. A plastic material is also used in each case for the manufacture of the pump head 12 and the pump block 20. The pump block 20 is welded to the support shield 54 in the area of the ring walls 50 and the support sleeves 58 surrounding these. Therefore, each ring wall 50 is connected by substance-to-substance bonding by way of a circumferential weld seam to a support sleeve 58 into which the ring wall 50 extends. This imparts a high mechanical stability to the ring walls 50 without these having to have a considerable material thickness.

With the support collars 60, the support shield 54 is supported in the axial direction on a guide shield 64 comprising a plurality of guide members in the form of guide sleeves 66 aligned coaxially with the longitudinal piston axes 52. A piston 24 lies slidingly against each guide sleeve 66. By means of a resetting spring 68 surrounding the guide sleeves 66 in each case, the pistons are pressed against a swash plate 70 which is mounted in a swash plate housing 72 for rotation about the longitudinal pump axis 18. The guide shield 64 forms a convexly outwardly curved cover for the swash plate housing 72 on which the guide shield 64 is supported in the axial direction.

The swash plate 70 can be rotated about the longitudinal pump axis 18 in the usual way by a drive motor, known per se and, therefore, not shown in the drawings, in particular, an electric motor, with the rotational movement of the motor shaft being transmitted by a gearing 74 shown schematically in FIG. 1 to the swash plate 70.

A high mechanical stability is achieved by the weld connection to a support sleeve 58, which surrounds a ring wall 50 in the circumferential direction, in each case, with the material usage being able to be kept relatively low for both the pump block 20 and the support shield 54. After the welding of the pump block 20 to the support shield 54, the sealing rings 46 surrounding one piston 24 each in the circumferential direction are reliably secured in both the axial and the radial direction, so that a high degree of tightness can be achieved by means of the sealing rings 46 even under high pressures. Liquid that does, nevertheless, leak from the pump chambers 22 can escape to the outside through the drainage slots 62.

To assemble the piston pump 10, it is possible, after assembly of the swash plate 70, for the guide shield 64 to be fitted on the swash plate housing 72, the pistons 24 having been previously inserted in the guide sleeves 66. The support shield 54 can then be fitted on the guide shield 64 after the suction valves 26 have been previously assembled in the pump block 20 and the pump block 20 has been welded to the support shield 54. The ring walls 50 surrounding one sealing ring 46 each in the circumferential direction thereby extend into the support sleeves 58. The ring walls 50 are welded to one support sleeve 58 each. Ultrasonic welding can be used for this purpose as both the pump block 20 and the support shield 54 are made of a plastic material.

After insertion of the pressure valves 28 and the central insert part 34 including the central closing member 44 into the pump block 20, in a following assembly step the pump head 12 can be fitted in the axial direction on the pump block 20, with an elastically deformable sealing ring 76 being positioned between the pump head 12 and the pump block 20. In a next assembly step, the pump head 12 can then be clamped to the pump block 20. A clamping element 77, for example, can be used for this purpose, which is shown only schematically in FIG. 1 and engages the end face 78 of the pump head 12 that faces away from the pump block 20. The clamping element 77 can engage over the pump head 12, the pump block 20 and the support shield 54 and be screwed to radially outwardly facing screw receptacles of the guide shield 64.

Manufacture and assembly of the piston pump 10 are, therefore, very simple. Use of the one-piece support shield 54 with the support sleeves 58 surrounding one ring wall 50 each and with the support collars 60 aligned coaxially with the support sleeves 58 makes it possible to keep the material usage of the support shield 54 and also the material usage of the pump block 20 in the area of the ring walls 50 low. 

1. A piston pump for a high-pressure cleaning appliance, said piston pump comprising a plurality of pump chambers into each of which one piston which is movable back and forth plunges, and which are each in flow connection via a suction valve with a suction inlet and via a pressure valve with a pressure outlet, the pistons each being surrounded by a sealing ring which is supported in the radial direction by a ring wall and in the axial direction by a support ring, and said piston pump comprising a one-piece support shield which forms the support rings and surrounds the ring walls in the circumferential direction.
 2. The piston pump in accordance with claim 1, wherein the support shield comprises a plurality of support sleeves into each of which a ring wall extends.
 3. The piston pump in accordance with claim 1, wherein the piston pump comprises a pump block which includes the pump chambers and is connected to the support shield by substance-to-substance bonding.
 4. The piston pump in accordance with claim 1, wherein the pump block is welded to the support shield.
 5. The piston pump in accordance with claim 2, wherein the ring walls are each welded to a surrounding support sleeve.
 6. The piston pump in accordance with claim 1, wherein the pump block and the support shield are made of a plastic material.
 7. The piston pump in accordance with claim 1, wherein the support shield is fitted on a guide shield comprising guide members for guiding the pistons in the axial direction.
 8. The piston pump in accordance with claim 7, wherein the support shield comprises support collars which are fitted on the guide shield and surround one piston each in the circumferential direction.
 9. The piston pump in accordance with claim 8, wherein the support collars comprise one drainage opening each. 